Which law states that a chemical compound always contains the same elements combined together in the same fixed proportion by mass?

Which of the following reactions is not correct according to law of conservation of mass

Which law implies that the mass ratio of elements in a compound is always a whole number ratio?

If two elements A and B combine in different ratios to form two compounds, the masses of B that combine with a fixed mass of A are in a small whole number ratio. This is a statement of:

Hydrogen and oxygen combine to form water (H2O). If 4g of hydrogen reacts completely with oxygen to form water, what mass of oxygen is required?

Which law explains why 18g of water always decomposes into 2g of hydrogen and 16g of oxygen?

When a solid vaporizes directly without melting, it is known as:

Which law explains the observation that 1g of hydrogen always combines with 8g of oxygen to form 9g of water?

A mixture of $CO$ and $CO_2$ weighing 1.12 g is treated with an excess of red hot $CuO$. The $CO$ is converted to $CO_2$. The total weight of $CO_2$ produced is 1.6 g. What was the weight percentage of $CO$ in the original mixture?

10 g of a metal oxide on strong heating gave 6.4 g of metal. If the formula of the metal oxide is $M_2O_3$, what is the atomic mass of the metal M?

Which law states that a chemical compound always contains the same elements combined together in the same fixed proportion by mass?